Polyurethane or polyurethane-urea aqueous dispersion, preparation method therefor, and use thereof

Abstract

A self-crosslinkable polyurethane or polyurethane-urea aqueous dispersion, a preparation method therefor, and a use thereof. Side chains of the polyurethane or polyurethane-urea contain non-sterically-hindered siloxy groups. During the drying and activation of the aqueous dispersion, the siloxys in the side chains are hydrolyzed and crosslinked with each other to increase the cross-linking density, significantly improving the heat resistance, the humidity resistance, and other properties of an adhesive obtained therefrom. The aqueous dispersion itself has a good stability. In addition, an application system based thereon has an excellent stability and a long storage time. The aqueous dispersion is suitable for the preparation of high quality paints and sealants, especially adhesives.

The invention claimed is: 
     
       1. A polyurethane or polyurethane-urea aqueous dispersion, wherein the polyurethane or polyurethane-urea aqueous dispersion is a reaction product obtained by reacting a composition comprising the following components:
 a) at least one silane component having a general formula of 
 
       
         
           
           
               
               
           
         
       
       wherein group R contains at least two NCO-reactive groups, wherein at least two of groups R 1 , R 2  and R 3  are methoxyls and/or ethoxyls, and the remaining groups R 1 , R 2  and/or R 3  is an alkyl;
 b) at least one polyol component having a functionality of 2-4, wherein the component b) comprises a mixture of a crystalline polyol having a number average molecular weight of 400-15,000 and at least one non-crystalline polyol having a number average molecular weight of 400-15,000; 
 c) at least one polyisocyanate component; 
 d) at least one hydrophilic compound component, the hydrophilic group of the hydrophilic compound comprises one or two of an ionic group and a potentially ionic group, the hydrophilic compound contains 2-3 NCO-reactive groups; 
 e) at least one NCO-reactive, monofunctional nonionic hydrophilic compound component; and 
 f) optionally, a compound containing 1-3 aminos and/or hydroxys in the molecule; and 
 g) optionally, other isocyanate-reactive compounds. 
 
     
     
       2. The aqueous dispersion according to  claim 1 , wherein based on the total weight of the composition, the component a) is used in an amount of 0.02-5 wt %; the component b) is used in an amount of 30-94 wt %; the component c) is used in an amount of 5-40 wt %; the component d) is used in an amount of 0.2-10 wt %; the component e) is used in an amount of 0.01-10 wt %; the component f) is used in an amount of 0-10 wt %; the component g) is used in an amount of 0-15 wt %. 
     
     
       3. The aqueous dispersion according to  claim 1 , wherein the NCO-reactive functional group of component a), the silane component is selected from the group consisting of hydroxy, primary aminos, secondary aminos and combinations thereof. 
     
     
       4. The aqueous dispersion according to  claim 1 , wherein component b) has a number average molecular weight of 20-15,000. 
     
     
       5. The aqueous dispersion according to  claim 1 , wherein component b) comprises a mixture of a crystalline diol having a number average molecular weight of 1,000-4,000 and a non-crystalline diol having a number average molecular weight of 1,000-4,000. 
     
     
       6. The aqueous dispersion according to  claim 5 , wherein the weight ratio of the crystalline diol to the non-crystalline diol is 1-25:1. 
     
     
       7. The aqueous dispersion according to  claim 1 , wherein the hydrophilic compound containing an ionic group or a potentially ionic group in the component d) comprises a component selected from the group consisting of dimethylolpropionic acid, dimethylolbutanoic acid, dimethylol acetic acid, dihydroxysuccinic acid, N-(2-aminoethyl)-2-aminoethanesulfonic acid, N-(3-aminopropyl)-2-aminoethanesulfonic acid, N-(3-aminopropyl)-3-aminopropanesulfonic acid, N-(2-aminoethyl)-3-aminopropanesulfonic acid and alkali metal salts, alkaline earth metal salts and ammonium salts thereof and combinations thereof. 
     
     
       8. The aqueous dispersion according to  claim 1 , wherein component e) has an ethylene oxide number of 4-200. 
     
     
       9. The aqueous dispersion according to  claim 1 , wherein the component f) is a compound containing 2-3 NCO-reactive functional groups, wherein at least one of the NCO-reactive functional groups is a primary amino or a secondary amino. 
     
     
       10. A method for preparing the aqueous dispersion as defined in  claim 1 , comprising the following steps: components b), c), d), e) and optionally g) react through a one-step or multi-step reaction to form a prepolymer with a terminal isocyanate, then the prepolymer reacts with component a) and optional f) through a one- or two-stage reaction, followed by water dispersion or dissolution, wherein a solvent which can be partially or completely removed by distillation during or after the dispersion is optionally used. 
     
     
       11. The aqueous dispersion according to  claim 1 , wherein the polyisocyanate component c) is a mixture of hexamethylene diisocyanate and isophorone diisocyanate with a weight ratio of 1-50:1 or a mixture of hexamethylene diisocyanate and 4,4′-dicyclohexylmethane diisocyanate with a weight ratio of 1-50:1, and
 the ionic group is carboxylate and/or sulfonate; the potentially ionic group is carboxyl and/or sulfonic group; and the NCO-reactive group is hydroxy and/or amino. 
 
     
     
       12. The aqueous dispersion according to  claim 2 , wherein based on the total weight of the composition, the component a) is used in an amount of 0.2-2.5 wt %; the component b) is used in an amount of 70-90 wt %; the component c) is used in an amount of 8-20 wt %; the component d) is used in an amount of 1-5 wt %; the component e) is used in an amount of 0.5-3 wt %; the component f) is used in an amount of 0.5-3 wt %; the component g) is used in an amount of 1-8 wt %. 
     
     
       13. The aqueous dispersion according to  claim 3 , wherein component a) is a silane having at least two primary aminos and/or secondary aminos. 
     
     
       14. The aqueous dispersion according to  claim 3 , wherein component a) is selected from the group consisting of N-β-(aminoethyl)-γ-aminopropyltrimethoxy silane, N-β-(aminoethyl)-γ-aminopropyltriethoxy silane and N-(β-aminoethyl)-γ-aminopropylmethyldimethoxy silane and combinations thereof. 
     
     
       15. The aqueous dispersion according to  claim 4 , wherein component b) comprises a component selected from the group consisting of a polyester polyol, a polycarbonate polyol, a polylactone polyol having a number average molecular weight of 500-5,000 and a functionality of 2-3, a small molecular alcohol having a number average molecular weight of 80-400 and a functionality of 2-4 and combination thereof. 
     
     
       16. The aqueous dispersion according to  claim 5 , wherein the non-crystalline diol is a polycarbonate diol prepared by the reaction of a component with dimethyl carbonate and/or diethyl carbonate, wherein the component is selected from the group consisting of 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol and combinations thereof; the crystalline diol is a polyester glycol prepared by the reaction of a component and adipic acid, wherein the component is selected from the group consisting of 1,4-butanediol, 1,6-hexanediol and combinations thereof. 
     
     
       17. The aqueous dispersion according to  claim 6 , wherein the weight ratio of the crystalline diol to the non-crystalline diol is 5-10:1. 
     
     
       18. The aqueous dispersion according to  claim 8 , wherein component e) is a monofunctional polyethoxy ether having a number average molecular weight of 200-8,000 and an ethylene oxide number of 4-200. 
     
     
       19. The aqueous dispersion according to  claim 8 , wherein component e) is a methoxy polyethylene glycol having a number average molecular weight of 500-3,000 and an ethylene oxide number of 12-75. 
     
     
       20. The aqueous dispersion according to  claim 9 , wherein the component f) is a mixture of isophoronediamine and N-(2-hydroxyethyl)ethylenediamine with a molar ratio of 0.5-10:1.